Effect of Process Parameters on Electrodeposited Nanocrystalline Chromium Coatings Investigated by an Orthogonal Experiment

The microporous nanocrystalline chromium coatings were prepared on the H13 steel by electroplating in self-regulating baths. The effects of electroplating parameters including current density, compositions of baths, bath temperature and plating time on the surface quality, thickness of chromium coating and cathode current efficiency were investigated by an orthogonal experiment. Experimental results indicated that the surface quality, thickness of chromium coating and cathode current efficiency can be improved by adjusting these electroplating parameters. Furthermore, bath temperature has the greatest effect on the surface quality of chromium coating, and the high qualified surfaces were only obtained at higher temperatures of 55 and 65°C. Current density was the most significant factor for the thickness of coating and cathode current efficiency. Chromium coating with high surface quality, thickness and cathode current efficiency was obtained at current density 90 A/dm2, CrO3 250 g/L, K2SiF6 10 g/L, SrSO4 1 g/L, bath temperature 65°C and plating time 120 min, which is consisting of pure nanocrystalline chromium with a body-centered cubic structure. And the coating exhibits much higher microhardness and corrosion resistance than for H13 steel.